1. Field of the Invention
This invention relates generally to apparatus and methods for producing heat exchange with body tissue, and more specifically to methods and apparatus for the hypothermic treatment of a body fluid in a body conduit.
2. Discussion of the Prior Art
Many of the advantages of hypothermia are well known. By way of example, it has been found particularly desirable to lower the temperature of body tissue in order to reduce the metabolism of the body. In stroke, trauma and several other pathological conditions, hypothermia also reduces the permeability of the blood/brain barrier. It inhibits release of damaging neurotransmitters and also inhibits calcium-mediated effects. Hypothermia inhibits brain edema and lowers intracranial pressure.
In the past, hypothermic treatment has been typically addressed systemically, meaning that the overall temperature of the entire body has been lowered to achieve the advantages noted above. This has been particularly desirable in surgical applications where the reduced metabolism has made it possible to more easily accommodate lengthy operative procedures. An example of this systemic approach includes catheters for transferring heat to or from blood flowing within a patient's vessel, as disclosed by Ginsburg in U.S. Pat. No. 5,436,208. A closed loop heat exchange catheter is also disclosed by Saab in U.S. Pat. No. 5,624,392. A cooling device for whole-body hyperthermia that utilizes the circulatory system of the body is known to be more efficient since the entire volume of the body is constantly perfused with the cold fluid at a capillary level.
Likewise, various other means of cooling the body have been tried with cooling blankets, ice water bladder lavages, ice baths, esophageal catheters and their associated methods. All of these devices require a considerable time to cool the body since the primary heat transfer occurs through the skin or the skull. A more efficient body cooling device that can quickly cool and accurately control the body temperature is required.